Method and apparatus for uniformly crimping a stent onto a catheter

ABSTRACT

A stent crimping tool for firmly and uniformly crimping a stent onto a balloon catheter is constructed from a crimping section holding the stent and the balloon catheter therein, wherein the crimping is actuated by a shaft having an input end and an output end, engaging the crimping section at the output end. The shaft has a detent formed into the input end. A gripping member has an internal cavity to receive the input end, and includes a hole proximate to the shaft, wherein a ball bearing and a compression spring are located within the hole to bias the ball bearing toward the shaft and to engage the detent. When a torque is applied to the gripping member, it is transmitted through the ball bearing to the shaft; if the torque exceeds a predetermined magnitude, it overcomes the force of the spring on the ball bearing causing the bearing to slide out of the detent thereby disconnecting the applied torque from the shaft. The crimping section can be a rubber tube having a lumen holding the stent and catheter. When the shaft compresses the rubber tube as it advances, the lumen collapses and crimps the stent onto the catheter. In another embodiment, the crimping section is a coiled filament suspended at both ends and having an axial space holding the stent and catheter. Rotating the shaft twists the filament which in turn constricts and crimps the stent onto the catheter.

This application is a continuation of U.S. Ser. No. 09/072,925, now U.S.Pat. No. 5,974,692, filed May 5, 1998.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for loading a tubulargraft, such as a stent, onto the distal end of a catheter assembly ofthe kind used, for example, in percutaneous transluminal coronaryangioplasty (PTCA) or percutaneous transluminal angioplasty (PTA)procedures.

In typical PTCA procedures, a guiding catheter is percutaneouslyintroduced into the cardiovascular system of a patient through thebrachial or femoral arteries and advanced through the vasculature untilthe distal end of the guiding catheter is in the ostium. A guide wireand a dilatation catheter having a balloon on the distal end areintroduced through the guiding catheter with the guide wire slidingwithin the dilatation catheter. The guide wire is first advanced out ofthe guiding catheter into the patient's coronary vasculature and thedilatation catheter is advanced over the previously advanced guide wireuntil the dilatation balloon is properly positioned across the arteriallesion. Once in position across the lesion, a flexible and expandableballoon is inflated to a predetermined size with a radiopaque liquid atrelatively high pressures to radially compress the atheroscleroticplaque of the lesion against the inside of the artery wall and therebydilate the lumen of the artery. The balloon is then deflated to a smallprofile so that the dilatation catheter can be withdrawn from thepatient's vasculature and the blood flow resumed through the dilatedartery. As should be appreciated by those skilled in the art, while theabove-described procedure is typical, it is not the only method used inangioplasty.

In angioplasty procedures of the kind referenced above, restenosis ofthe artery may develop over time, which may require another angioplastyprocedure, a surgical bypass operation, or some other method ofrepairing or strengthening the area. To reduce the likelihood of thedevelopment of restenosis and to strengthen the area, a physician canimplant an intravascular prosthesis for maintaining vascular patency,commonly known as a stent, inside the artery at the lesion. The stent iscrimped tightly onto the balloon portion of the catheter and transportedin its delivery diameter through the patient's vasculature. At thedeployment site, the stent is expanded to a larger diameter, often byinflating the balloon portion of the catheter. The stent also may be ofthe self-expanding type.

Since the catheter and stent travel through the patient's vasculature,and probably through the coronary arteries, the stent must have a smalldelivery diameter and must be firmly attached to the catheter until thephysician is ready to implant it. Thus, the stent must be loaded ontothe catheter so that it does not interfere with delivery, and it mustnot come off the catheter until it is implanted.

In procedures where the stent is placed over the balloon portion of thecatheter, it is necessary to crimp the stent onto the balloon portion toreduce its diameter and to prevent it from sliding off the catheter whenthe catheter is advanced through the patient's vasculature. Non-uniformcrimping can result in sharp edges being formed along the now unevensurface of the crimped stent. Furthermore, non-uniform stent crimpingmay not achieve the desired minimal profile for the stent and catheterassembly. Where the stent is not reliably crimped onto the catheter, thestent may slide off the catheter and into the patient's vasculatureprematurely as a loose foreign body, possibly causing blood clots in thevasculature, including thrombosis. Therefore, it is important to ensurethe proper crimping of a stent onto a catheter in a uniform and reliablemanner.

This crimping is often done by hand, which can be unsatisfactory due tothe uneven application of force resulting in non-uniform crimps. Inaddition, it is difficult to visually judge when a uniform and reliablecrimp has been applied.

Some self-expanding stents are difficult to load by hand onto a deliverydevice such as a catheter. Furthermore, the more the stent is handledthe higher the likelihood of human error, which is antithetical to aproperly crimped stent. Accordingly, there is a need in the art for adevice for reliably crimping a stent onto a catheter.

There have been attempts at devising a tool for crimping a stent onto aballoon delivery catheter. An example of such a tool comprises a seriesof plates having substantially flat and parallel surfaces that move in arectilinear fashion with respect to each other. A stent carryingcatheter is disposed between these surfaces, which surfaces crimp thestent onto the outside of the catheter by their relative motion andapplied pressure. The plates have multiple degrees of freedom and mayhave force-indicating transducers to measure and indicate the forceapplied to the catheter during crimping of the stent.

Another stent loading tool design is comprised of a tubular memberhousing a bladder. The tubular member and bladder are constructed tohold a stent that is to be crimped onto a balloon catheter assembly.Upon placement of the stent over the balloon portion of the catheter, avalve in the loading tool is activated to inflate the bladder. Thebladder compresses the stent radially inward to a reduced diameter ontothe balloon portion of the catheter to achieve a snug fit. In this way,the stent is crimped onto the distal end of a balloon catheter with aminimum of human handling. The foregoing stent crimping tools aredisclosed in, for example, U.S. Pat. Nos. 5,437,083 and 5,546,646 toWilliams et al.

Yet another stent crimping tool is known in the art as the BARD XT,which is actually a stent loader. It is constructed from a rigid,tubular body with a ball at one end connected to a plurality of long,thin strips passing through the tubular body. An uncrimped stent isplaced over the plurality of long, thin strips, which hold the stent inan expanded state. The balloon portion of a catheter is inserted intothe cylindrical space formed by the plurality of strips. When the userpulls the ball while holding the tubular body against the stent, thestrips are slid from beneath the stent and the stent is transferred ontothe balloon portion.

Still another conventional stent crimping tool is manufactured byJOHNSON & JOHNSON and appears similar to a hinged nutcracker.Specifically, the tool is comprised of two hand operated levers hingedat one end and gripped in the palm of the hand at the opposite end. Acylindrical opening holding a crimping tube is provided through themid-portion of the tool to receive therein a stent loaded onto a ballooncatheter. The crimping operation is performed by the user squeezing thehandle thereby pressing the crimping tube which in turn pinches thestent onto the balloon catheter.

While the prior art devices are suitable for crimping stents ontoballoon catheters, they suffer from problems such as non-uniformcrimping forces, resulting in non-uniform crimps. Consequently, they areunsuitable for use by physicians in a cath lab who desire to crimp thestent onto the balloon catheter.

SUMMARY OF THE INVENTION

Both PTCA and PTA procedures have become commonplace in treatingstenoses or lesions in blood vessels and coronary arteries. Inapproximately 35% to 40% of the procedures, restenosis may developrequiring a further angioplasty, atherectomy or bypass procedure toreturn the patency of the vessel. Intravascular stents are now beingdeployed after PTCA and PTA procedures, and after atherectomies, inorder to help prevent the development of restenosis. Importantly, suchstents, mounted on the balloon portion of a catheter, must be tightlycrimped to provide a low profile delivery diameter, and to ensure thatthe stent stays on the balloon until the balloon is expanded and thestent is implanted in the vessel. The present invention is directed to acrimping tool that can repeatedly provide a uniform and tight crimp toensure the low profile diameter of the stent on the balloon portion ofthe catheter, and to ensure that the stent remains firmly attached untilit is implanted in the vessel by expanding the balloon.

The present invention is directed to a method and apparatus to obtainconsistent crimping of a stent on a balloon catheter independent of theballoon profile. This is accomplished by limiting the amount of forcethat is applied to crimp the stent by using a clutch that disconnectsthe applied torque at a predetermined level.

In particular, the present invention is directed to a tool for crimpinga stent onto a balloon catheter, comprising a crimping section holdingthe stent and the balloon catheter therein; a shaft having an input endand an output end, engaging the crimping section at the output end,which shaft when rotated actuates the crimping section to crimp thestent; a detent formed into the input end of the shaft; a grippingmember having an internal cavity to receive the input end of the shaft,wherein the cavity includes a hole proximate to the shaft; a stopmember; a biasing member disposed in the hole and biasing the stopmember into engagement with the detent; whereby applying a torque to thegripping member beyond a predetermined level overcomes the force of thebiasing member and slides the stop member out of the detent to disengagethe applied torque from the shaft.

Rotation of the shaft halts, and the magnitude of the crimping forceencountered by the stent levels off or drops off due to resilience orbacklash in the system. Damage to the stent from excessive crimpingforce is avoided.

In one exemplary embodiment, the crimping section comprises a housinghaving an internal chamber with an enclosed first end, and an opensecond end having threads, wherein the output end of the shaft ispartially disposed within the internal chamber through the open secondend of the housing, and wherein the input end of the shaft includesthreads that engage the threads of the internal chamber; and an elastictubing having a lumen, wherein the tubing is disposed within theinternal chamber adjacent the enclosed first end, and the output end ofthe shaft is disposed adjacent the tubing. Accordingly, the stent andballoon catheter are positioned within the lumen and rotation of theshaft advances the shaft into the tubing, compressing the tubing, andcrimping the stent.

In another exemplary embodiment, the crimping section comprises a rigidchassis having a hollow interior enclosed by a closed back end andleading to an open front end, wherein the back end includes a threadedopening; an end cap enclosing the open front end, the end cap includinga central opening; an elastic tube disposed within the hollow interioradjacent to the front end and having a length less than a length of thehollow interior to define a chamber adjacent to the back end; a pistonslidably disposed within the chamber; wherein the shaft passes throughthe closed back end of the chassis and the shaft includes threadsengaging the threads of the back end, and the output end of the shaftengages the piston so that the shaft when rotated displaces the pistonto compress the elastic tube; whereby the stent is loaded onto thecatheter and is inserted through the central opening into the elastictube, and the compressed elastic tube squeezes the stent radially ontothe catheter.

In yet another exemplary embodiment, the crimping section comprises abase having at least first and second spaced apart supports, wherein theshaft is rotatably disposed on the second support with the output end ofthe shaft extending toward the first support; a coiled filament havingan axial space and being attached to the first support and the outputend of the shaft and extending between the first and second supports;whereby inserting the stent and catheter into the axial space of thecoiled filament and rotating the shaft reduces the diameter of the axialspace thereby crimping the stent onto the catheter.

In conclusion, it is clear that the present invention tool can beadapted to a variety of stent crimping sections that are operated byapplication of torque. The clutch of the present invention ensures thatthe amount of force applied during the crimping process is controlled.This is achieved by disconnecting the gripping member from the shaft ata predetermined level of torque. Doing so disrupts the transfer oftorque to the crimping section of the tool, which in turn levels theamount of crimping force exerted on the stent.

With precise control of applied crimping forces, the present inventiontool is capable of homogeneously crimping a stent onto a ballooncatheter. Such a crimping tool is highly useful to cardiologists, forexample. Such physicians are often concerned with proper deployment ofthe stent within the patient that it is desirable to have a consistentlyand reliably crimped stent. The present invention tool is further a timesaver, because the stent crimping procedure can be performed fairlyefficiently and quickly. These and other advantages of the presentinvention will become apparent from the following detailed descriptionthereof when taken in conjunction with the accompanying exemplarydrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view, partially in section, depicting astent that has been crimped onto a delivery catheter and disposed withina vessel.

FIG. 2 is a sectional view of a preferred embodiment of the presentinvention, showing the clutch mechanism and the crimping section of thetool.

FIG. 3 is a cross-sectional view of an alternative embodiment of thepresent invention tool shown in FIG. 2.

FIG. 4 is a perspective view of an exemplary embodiment tool wherein thecrimping section includes a coiled filament used to crimp the stent.

FIGS. 5 and 6 are simplified schematic diagrams depicting a stentcrimping operation performed by the present invention tool.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates intravascular stent 10 which is mounted onto deliverycatheter 11. Stent 10 generally comprises a plurality of radiallyexpandable cylindrical elements 12 disposed coaxially and interconnectedby members 13 disposed between adjacent cylindrical elements 12.Delivery catheter 11 has an expandable portion or balloon 14 forexpanding stent 10 within coronary artery 15 or other vessel such assaphenous veins, carotid arteries, arteries, and veins. Artery 15, asshown in FIG. 1, has dissected lining 16 which has occluded a portion ofthe arterial passageway.

Delivery catheter 11 onto which stent 10 is mounted is essentially thesame as a conventional balloon dilatation catheter for angioplastyprocedures. Balloon 14 may be formed of suitable materials such aspolyethylene, polyvinyl chloride, polyethylene terephthalate and otherlike polymers. In order for stent 10 to remain in place on balloon 14during delivery to the site of the damage within artery 15, stent 10 iscompressed onto balloon 14.

An optional retractable protective delivery sleeve 20 may be provided tofurther ensure that stent 10 stays in place on balloon 14 of deliverycatheter 1 1 and to prevent abrasion of the body lumen by the opensurface of stent 10 during delivery to the desired arterial location.Other means for securing stent 10 onto balloon 14 may also be used, suchas providing collars or ridges on the ends of the working portion, i.e.,the cylindrical portion of balloon 14.

In order to implant stent 10, it is first mounted onto inflation balloon14 on the distal extremity of delivery catheter 11. Stent 10 is crimpeddown onto balloon 14 to ensure a low profile. The present inventionaddresses this crimping procedure.

The catheter-stent assembly can be introduced into the patient'svasculature through processes known in the art. Briefly, guide wire 18is disposed across the arterial section where an angioplasty oratherectomy has been performed requiring a follow-up stenting procedure.In some cases, the arterial wall lining may be detached so that guidewire 18 is advanced past detached or dissected lining 16 and thecatheter-stent assembly is advanced over guide wire 18 within artery 15until stent 10 is directly under detached lining 16. Prior to inflationof balloon 14, optional delivery sleeve 20 is retracted to expose stent10. Depending on the balloon and stent assembly, a delivery sleeve maybe unnecessary. Balloon 14 of delivery catheter 11 is then inflatedusing an inflation fluid. Expansion of balloon 14 in turn expands stent10 against artery 15. Next, balloon 14 is deflated and catheter 11 iswithdrawn leaving stent 10 to support the damaged arterial section. Asmentioned above, in order to ensure proper seating of stent 10 onballoon 14, and to ensure proper deployment of stent 10 at the site ofthe damage within artery 15, the stent crimping procedure is important.

FIG. 2 is a cross-sectional view of a preferred embodiment of thepresent invention stent crimping tool 22. Stent crimping tool 22 asshown preferably has crimping section 24 and actuation section 26.Actuation section 26 is rotated and torque is transmitted through shaft28 to crimping section 24.

In order to limit the amount of torque transmitted to shaft 28 and tothus limit the amount of crimping force, the present invention includesa clutch mechanism. In the preferred embodiment, the clutch mechanismincludes compression spring 30, ball bearing 32, and detent 34 locatedon shaft 28. As gripping member 36, which can be a knob, crank, knurledspindle, or the like, is rotated, torque is transmitted through a stopmember, here ball bearing 32, to detent 34. Spring 30 which ispositioned within hole 38 biases ball bearing 32 into detent 34 withsufficient force to maintain the transfer of torque from gripping member36 to shaft 28. If, however, a predetermined amount of torque isexceeded, the axial force of compression spring 30 is overcome causingball bearing 32 to slide out of detent 34 and to retract into hole 38.Of course, this predetermined amount of torque can be adjusted bymodifying the spring force, depth of the detent, size of the ballbearing, and other parameters known in the art.

At that instant, the linkage between gripping member 36 and shaft 28 isbroken because ball bearing 32 is free to rotate and slide along theouter circumference of shaft 28. The clutch mechanism thus limits thetorque delivery through shaft 28 into crimping section 24.

In the exemplary embodiment shown in FIG. 2, detent 34 is asemi-spherical cut-out formed in the input end 40 of shaft 28. Input end40 is also received within cavity 42 of gripping member 36. Grippingmember 36 may be formed in a cylindrical shape for easy gripping asshown, or may take other grippable shapes known in the art. Furthermore,a resilient piece of material may be used to replace spring 30 to biasball bearing into shaft 28. For example, a sponge-like material can beused that has compliance and a level of resilience needed to urge ballbearing 32 into detent 34 in order to transfer torque between grippingmember 36 and shaft 28.

At the opposite end of shaft 28 is output end 44 which is preferablylocated adjacent resilient tubing 46. Shaft 28 further includes externalthreads 48 meant to engage internal threads 50 formed inside housing 52of crimping section 24. Resilient tubing 46 fits within hollow interior54 of housing 52, wherein the latter is sufficiently rigid to not expandor distort under pressure. At the opposite end of housing 52 is end cap56 that encloses the back end.

Thus, as the user manually rotates shaft 28 through application oftorque to gripping member 36, shaft 28 advances into and compressesresilient tubing 46. Within resilient tubing 46 is lumen 58 containinguncrimped stent 10 already loaded onto balloon 14 of catheter 11. Endcap 56 has an optional central opening 60 in communication with lumen58. Hence, delivery catheter 11 can be inserted through central opening60 and advanced into alignment with uncrimped stent 10 inside lumen 58.As compression of the resilient tubing 46 takes place, the length ofresilient tubing 46 is shortened thereby causing lumen 58 to collapseand simultaneously crimp stent 10 onto delivery catheter 11. After thecrimping step, shaft 28 is rotated in the opposite direction to retractit away from resilient tubing 46, which regains its original shape.Thereafter, the crimped stent and catheter assembly can be withdrawnthrough central opening 60.

In an alternative embodiment, a through hole (not shown) can be formedthrough the length of shaft 28 and through gripping member 36. After thecrimping step, the crimped stent and catheter assembly can be advancedover a guide wire (not shown), passing through the through hole, and outthe opposite end of the tool. Therefore, in this alternative embodiment,the crimped stent and catheter assembly can be immediately advanced overthe guide wire to the patient for implantation after the crimping step.

During the crimping step, if maximum torque is exceeded, as explainedabove, ball bearing 32 slides out of detent 34. On the other hand, ifgripping member 36 is continuously rotated, ball bearing 32 can bereseated within detent 34 during a subsequent revolution of grippingmember 36 about input end 40, thereby re-engaging the linkage betweenshaft 28 and gripping member 36. At that moment, torque can be reappliedby rotating the gripping member 36 in either direction to advance orretract shaft 28. By alternately advancing and retracting shaft 28, itis possible to repeat the crimping step and ensure a firm and consistentcrimp of stent 10 on catheter 11. To be sure, it is also possible torotate delivery catheter 11 during each cycle of the crimping step.

FIG. 3 is an alternative embodiment of the exemplary embodiment shown inFIG. 2. More precisely, FIG. 3 is a cross-sectional view showingcrimping section 62 that is a modification of crimping section 24 fromFIG. 2. As seen in FIG. 3, torque is transferred between gripping member36 and crimping section 62 through threaded shaft 64. Crimping section62 is similar to that disclosed in co-pending U.S. patent applicationentitled "Indeflator-Driven, Rubber-Compression Crimping Tool" byStephen A. Morales, (ACS-42071) Ser. No. 09/063,905, filed Apr. 21,1998, whose entire contents are incorporated herein by reference.

In this embodiment, crimping section 62 is constructed from cylindricalshape chassis 66 having open end 68 and closed end 70. Open end 68 issealed closed with optional end cap 72 that is bonded to open end 68using adhesive 74 of a type known in the art. Optionally, end cap 72 maybe attached to chassis 66 using threads, snaps, clamps, or othermechanical means known in the art.

Within cylindrical shape chassis 66 is hollow interior 76 that containselastic tube 78 that is coaxially disposed within chassis 66. Notably,elastic tube 78 has a length that is shorter than the length of hollowinterior 76. Because of this difference in length, and because elastictube 78 is disposed adjacent open end 68, chamber 80 is formed adjacentto closed end 70. Slidably disposed within chamber 80 is movable piston82. Shaft 64 engages piston 82 as shown in FIG. 3.

End cap 72 includes central opening 84 that is aligned and incommunication with axial space 86 of elastic tube 78. Central opening 84allows the stent-catheter assembly to be inserted into crimping section62 prior to undergoing the crimping procedure.

Leading up to the procedure, a user introduces stent 10 already loadedonto balloon portion 14 of catheter 11 into axial space 86 withinelastic tube 78. In the exemplary embodiment, the inside diameter ofelastic tube 78 is slightly greater than the outside diameter of theuncrimped stent 10, or uncrimped stent and balloon 10 and 14,respectively.

As gripping member 36 is rotated, torque is transmitted through spring30 to ball bearing 32 and to the walls of detent 34 formed in shaft 64.Shaft 64 once in rotation advances piston 82 into elastic tube 78 asindicated by the arrow. As a result, elastic tube 78 is compressedaxially or lengthwise. The elastic material of elastic tube 78 mustmaintain a constant volume due to its surface elasticity and containmentwithin the confines of hollow interior 76. Continuous compression ofelastic tube 78 by piston 82 causes the material of elastic tube 78 todisplace axially and then radially into axial space 86, in effectcollapsing that space. This decreases the diameter of axial space 86. Inturn, stent 10 contained inside axial space 86 is compressed radiallyonto balloon portion 14 of catheter 11.

As in the previously described embodiment, exceeding a pre-determinedtorque on gripping member 36 disengages ball bearing 32 from detent 34to disconnect the application of torque to shaft 64. On the other hand,insofar as gripping member 36 and shaft 64 are linked through the clutchmechanism, it is possible to rotate and counter-rotate shaft 64 toadvance and retract, respectively, piston 82. Indeed, it is possible tocycle through the crimping step over and over as necessary.

In the various exemplary embodiments of the present invention crimpingtool shown in FIGS. 2 and 3, the housing pieces, piston, shafts,gripping member, etc. can be made from a rigid, injection molded plasticmaterial. Also, translucent and transparent materials can be used sothat the task at hand can be visually monitored. The present inventiondesign is well suited for fabrication from surgical steel, too.Resilient tubing 46 and elastic tube 78 of each embodiment can be madefrom rubber or other elastomers known in the art.

FIG. 4 is a perspective view of an alternative embodiment of the presentinvention tool. In this embodiment, stent crimping section 90 contains afilament used to constrict a stent onto a balloon catheter insertedwithin an axial space formed by the coiled filament. Torque is stillapplied through gripping member 36, which is connected to shaft 92. Asbest seen in this figure, the surface of gripping member 36 mayoptionally be contoured or knurled by pattern 94 to provide a bettergripping surface.

Stent crimping section 90 is similar to that disclosed in co-pendingU.S. patent application entitled "Stent Crimping Tool and Method of Use"by Stephen A. Morales, (ACS-42070) Ser. No. 08/962,632, filed Nov. 3,1997, the entire contents of which are incorporated herein by reference.In FIG. 4, stent crimping section 90 includes base 96, first verticalsupport 98, second vertical support 100, wherein the two verticalsupports 98 and 100 are spaced apart on base 96. Shaft 92 rotatablypasses through an opening in second vertical support 100. Cam 102 isaffixed on shaft 92 whereby the cam rotates with shaft 92.

Cam 102 optionally includes an obstruction which, in the preferredembodiment, are teeth 104 located at the circumference of cam 102 andare designed to engage pawl 106. Pawl 106 is positioned on base 96 andbiased into teeth 104. Together, cam 102, teeth 104, and pawl 106 form aratchet mechanism that permits rotation in one direction yet preventsrotation of shaft 92 in the opposite direction.

Attached to output end 108 of shaft 92 is one end of coiled filament110. The opposite end of coiled filament 110 is connected to firstvertical support 98. In the preferred embodiment shown in FIG. 4, coiledfilament 110 is a coiled tension spring with its ends hooked to pins 112and 114.

In FIG. 4, the present invention tool has fairly high extending verticalsupports 98, 100, such that shaft 92 passes through second verticalsupport 100 rather than just resting upon it. Optional bearing 116 islocated inside second vertical support 100 to minimize rotationalfriction between shaft 92 and second vertical support 100.

Also, through hole 118 is provided in first vertical support 98 and isin communication with axial space 120 that is defined by the collectionof coils of coiled filament 110. When the tool is used, through hole 118allows the stent-catheter assembly to be passed therethrough into axialspace 120.

FIGS. 5 and 6 are simplified schematic diagrams of the preferredembodiment of the present invention shown in FIG. 4 to help explain thecrimping operation. Specifically, FIG. 5 provides a side elevationalview of the present invention whereby stent 10 and balloon 14 have beeninserted within axial space 120. Optional sheath 122 is shown coveringthe stent-catheter assembly. Inside gripping member 36, ball bearing 32has been biased by compression spring 30 into detent 34. Gripping member36 can be rotated to apply torque through shaft 92 thereby twistingcoiled filament 110 in order to constrict the stent-catheter assemblyinside axial space 120.

FIG. 6 shows completion of the crimping step after coiled filament 110has been twisted. Also shown in FIG. 6 is the instant when maximumtorque has been exceeded so that ball bearing 32 has slid out of detent34 and is riding on the outside diameter of shaft 92. At this veryinstant, the applied torque from gripping member 36 is disconnected fromshaft 92 and from constricted coiled filament 110. The naturalresiliency of coiled filament 110 at this moment tends to counter-rotateshaft 92. However, pawl 106 biased by spring 124 engages cam 102 toprevent the counter-rotation. Of course, disengagement of pawl 106 fromcam 102 would permit free rotation of shaft 92 in either direction. Atinput end 126 of shaft 92, shaft 92 rotates independently of grippingmember 36 until ball bearing 32 is again seated within detent 34 duringone of the revolutions of shaft 92 relative to gripping member 36. Uponre-engagement, gripping member 36 is again linked to shaft 92 to controlits rotation.

In the preferred embodiment, parts forming crimping section 90 are madefrom Nylon or a comparable polymer known in the art. Coiled filament 110can be a metal tension spring, a resilient polymer ribbon made fromMylar, for example, formed into a coil. The coiled filament can have aflat, polygonal, or round cross-sectional shape.

The present invention is preferably sterilized and intended to be usedin a cath lab by a trained technician or cardiologist. As will beappreciated by those skilled in the art, the present invention crimpingtool is designed both for single use applications in a cath lab by aphysician, or for multiple use applications in a sterile environment ina high volume manufacturing facility. In such a manufacturing facilitywhere sterile conditions exist, the present invention stent crimpingtool can be used repeatedly to crimp stents onto balloons until themechanism wears out. Thus, repeated uses of the present invention arecontemplated for controlled, sterile environments, as are single useapplications when operated by cath lab personnel.

Furthermore, the present invention crimping tool can be used with anystent that is released without a delivery system. The crimping tool mayalso be sold alone, because its design is robust enough to undergo manyuses.

Other modifications can be made to the present invention withoutdeparting from the scope thereof. The specific dimensions, proceduralsteps, and materials of construction are provided as examples, andsubstitutes are readily contemplated which do not depart from theinvention.

What is claimed is:
 1. A stent crimping tool, comprising:a crimpingsection holding the stent and the balloon catheter therein; a shafthaving an input end and an output end, engaging the crimping section atthe output end, which shaft when rotated actuates the crimping sectionto crimp the stent; a detent formed into the input end of the shaft; agripping member having an internal cavity to receive the input end ofthe shaft, wherein the cavity includes a hole proximate to the shaft; astop member; a biasing member disposed in the hole and biasing the stopmember into engagement with the detent; a base having at least first andsecond spaced apart supports; wherein the shaft is rotatably disposed onthe second support with the output end of the shaft extending toward thefirst support; a coiled filament having an axial space and beingattached to the first support and the output end of the shaft andextending between the first and second supports; whereby inserting thestent and catheter into the axial space of the coiled filament androtating the shaft reduces the diameter of the axial space therebycrimping the stent onto the catheter.
 2. The stent crimping toolaccording to claim 1, wherein the coiled filament includes a coiledspring.
 3. The stent crimping tool according to claim 1, wherein thecoiled filament includes a flat cross-sectional shape.
 4. The stentcrimping tool according to claim 1, wherein the crimping tool furthercomprises:a cam affixed to the shaft and having an obstruction at acircumference thereof; and a pawl disposed on the base and biased in toengagement with the cam obstruction to prevent free rotation of theshaft.
 5. The stent crimping tool according to claim 1, wherein the toolfurther includes a sheath at least partially covering the stent andcatheter.